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A few instances of injury/death were reported when passengers/pilots got partially sucked out of the airplane due to cabin depressurisation in a commercial aircraft. Paratroopers, on the other hand, do this all the time. When the bay doors open, they don't get sucked out. Rather, they jump off on their own. What is the difference in the two scenarios?

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    $\begingroup$ When I did my first jump (civilian) from a Cessna I almost got sucked out. $\endgroup$
    – d-b
    Nov 16, 2022 at 0:59
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    $\begingroup$ If the cabin pressure is higher than the environment pressure, they are blown out, not sucked. $\endgroup$
    – Uwe
    Nov 17, 2022 at 15:02
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    $\begingroup$ @Uwe: you appear to be saying that being sucked out of anything is a physical impossibility. $\endgroup$
    – TonyK
    Nov 17, 2022 at 19:11

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The difference is in the pressurization. An aircraft with skydivers or paratroopers would either not pressurize in the first place or smoothly depressurize the cabin using the outflow valve before opening the bay door. Therefore, there is no pressure difference when the door is opened.

When people are sucked out of a window, this is due to a rapid depressurization event. The aircraft was pressurized with respect to the outside air and when the window fails a lot of air is rushing out in a short amount of time to equalize the pressure.

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    $\begingroup$ From what i have seen, even very high jumps don't exceed 9000 meters altitude. The pressure on that level is still comfortable for a human body (you will only need an oxygen supply). People climb Mount Everest without any pressure suits, which has an altitude of 8848 meters. $\endgroup$
    – dunni
    Nov 15, 2022 at 10:57
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    $\begingroup$ People have even climbed Mt Everest without oxygen. That's many hours spent at that altitude. Jumping from that altitude is likely survivable without oxygen, as it just takes a few minutes to descend to a thicker atmosphere. $\endgroup$
    – MSalters
    Nov 15, 2022 at 13:01
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    $\begingroup$ @MSalters They also take several weeks to acclimate to that. If you were at a comfortable altitude (say, 3000 meters) and suddenly got shot out to Mt. Everest-level pressurization, I bet it would be pretty rough on you — at a time when you probably want to be in tip-top mental shape (which is not the case of Everest climbers without oxygen). According to wikipedia, they carry oxygen for the jump. $\endgroup$
    – yshavit
    Nov 15, 2022 at 21:27
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    $\begingroup$ This is the correct answer despite whatever details may surface about rapid shifts in pressurization. I expect paratroopers who jump at high altitudes train for it. Frankly, Hollywood makes the whole situation seem a lot worse than it actually is. Pop a window and half the plane is sucked out... And there's always at least one who's pulled into an engine. But never the heroine or hero who just stands there shooting the villain who probably broke the window on a wild shot anyway... Funny that. $\endgroup$
    – JBH
    Nov 15, 2022 at 22:28
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    $\begingroup$ @ScottishTapWater British Airways Flight 5390: "an improperly installed windscreen panel separated from its frame causing the captain to be sucked out of the aircraft" $\endgroup$
    – Bianfable
    Nov 16, 2022 at 18:09
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The interior of highflying airplanes is pressurized from the inside because there's not enough air at that altitude. For parachuting, you wouldn't want to fly at those altitudes anyway, unless you're doing a HALO jump, in which case the plane would be de-pressurized safely before the drop and the crew just wear oxygen masks. For lower altitude flights, you just open the door and jump out, because there's no pressure differential: enter image description here Paratroops are dropped from the lowest possible safe altitude, because the point is to get down ASAP, not recreational skydiving.

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The key point:

You can't open the door on an aircraft when it's pressurized.

If you have even a mild 3 PSI (20kPa) pressuration and a modestly sized aircraft side door of 2000 square inches (2 sq.m.?), that is 6000 pounds (3 tonne) of pressure on that door. As such, most aircraft doors are designed to open inward (at least for the first few mm, e.g. via an over-center arrangement). That way, the outward pressure helps pin the door mechanism in the shut position, using the pressure to prevent accidental opening. It can also help seat the seals, and place the door's weight on more sturdy elements, reducing mechanism wear.

You cannot possibly open an inward-moving door at pressure. Even if the door is outward-moving and you manage to overpower the over-center mechanism, the door would open extremely violently due to the many tonnes of force on the door. This would damage mechanism, door, frame and even possibly down the aircraft.

So with no pressure difference, there is no "rush of air blasting out of the now-opened door".

This settles the crux of your question:

How do parachuters jump out of a pressurized aircraft? They don't.

When aircraft are set up for parachuting, they depressurize the aircraft. This is a prerequisite to opening any door. Now, jetliner doors aren't really made to be opened in flight, but it actually works on the 727's rear door, as famously used by D.B. Cooper. And of course, military cargo airplanes with rear doors are designed to do the same, to allow cargo drops and paratroopers. And likewise civilian jump aircraft.

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    $\begingroup$ It is precisely because of DB Cooper that modern passenger jets no longer have doors in the tail assembly. $\endgroup$
    – Dúthomhas
    Nov 16, 2022 at 21:32

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